After years as a private commemoration, the anniversary of Sept. 11 at ground zero now also has become an occasion for public reflection on the site of the terror attacks.

An estimated 20,000 people flocked to the memorial plaza on the evening of Sept. 11 last year, the first year the public was able to visit on the anniversary. The plaza will open three hours earlier after Friday's 14th anniversary ceremony, where victims' families will gather for what has become a tradition of tolling bells, observing poignant moments of silence and reading the names of the nearly 3,000 people killed in the terror strike.

"When we did open it up, it was just like life coming in," National Sept. 11 Memorial and Museum President Joe Daniels said this week. While the memorial will still be reserved for victims' relatives and other invitees during the morning ceremony, afterward, "the general public that wants to come and pay their respects on this most sacred ground should be let in as soon as possible."

Nearly a decade and a half after hijacked planes hit the World Trade Center's twin towers, the Pentagon and a field near Shanksville, Pennsylvania, the anniversary continues to be marked with observances around the country.

The Flight 93 National Memorial near Shanksville in western Pennsylvania is marking the completion of its visitor center, which opened to the public Thursday. At the Pentagon, Secretary of Defense Ash Carter and other officials will join in remembrances for victims' relatives and Pentagon employees.

President Barack Obama is scheduled to observe the anniversary with a visit to Fort Meade, Maryland, in recognition of the military's work to protect the country.

Ohio's statehouse will display nearly 3,000 flags - representing the lives lost - in an arrangement designed to represent the World Trade Center towers, with a Pentagon-shaped space and an open strip representing the field near Shanksville. Sacramento, California, will commemorate 9/11 in conjunction with a parade honoring three Sacramento-area friends who tackled a heavily armed gunman on a Paris-bound high-speed train last month.

In Washington, some members of Congress plan to spend part of the anniversary discussing federal funding for the ground zero memorial. The House Natural Resources Committee has scheduled a hearing Friday on a proposal to provide up to $25 million a year for the plaza.

The memorial and underground museum together cost $60 million a year to run. The federal government contributed heavily to building the institution; leaders have tried unsuccessfully for years to get Washington to chip in for annual costs, as well.

Under the current proposal, any federal money would go only toward the memorial plaza. An estimated 21 million people have visited it for free since its 2011 opening.

The museum charges up to $24 per ticket, a price that initially sparked some controversy. Still, almost 3.6 million visitors have come since the museum's May 2014 opening, topping projections by about 5 percent, Daniels said.

Any federal funding could lead to expanded discounts for school and other groups, but there are no plans to lower the regular ticket price, he said.

This year's anniversary also comes as advocates for 9/11 responders and survivors are pushing Congress to extend two federal programs that promised billions of dollars in compensation and medical care. Both programs are set to expire next year.

But some of those close to the events aim to keep policy and politics at arm's length on Sept. 11.

Organizers of the ground zero ceremony decided in 2012 to stop letting elected officials read names, though politicians still can attend. Over the years, some victims' relatives have invoked political matters while reading names - such as declaring that Sept. 11 should be a national holiday - but others have sought to keep the focus personal.

"This day should be a day for reflection and remembrance. Only," Faith Tieri, who lost her brother, Sal Tieri Jr., said during last year's commemoration.